The chicken (Gallus gallus, sometimes G. gallus domesticus) is a domesticated fowl. Recent evidence suggests that domestication of the chicken was under way in Vietnam over 10,000 years ago. Until this discovery, conventional wisdom held that the chicken was domesticated in India. From India the domesticated fowl made its way to Persia. From the Persianised kingdom of Lydia in western Asia Minor, domestic fowl were imported to Greece perhaps as late as the fifth century BC. Fowl had been known in Egypt since the 18th Dynasty, the “bird that lays every day” having come to Egypt, according to the annals of Tutmose III, as tribute from from the land between Syria and Shinar, that is Babylonia. Fowl make no appearance in the Old Testament.

Some genetic research has suggested that the bird likely descended from both Red and the Grey Junglefowl (G. sonneratii). Although hybrids of both wild types usually tend toward sterility, recent genetic work has revealed that the genotype for yellow skin present in the domestic fowl is not present in what is otherwise its closest kin, the Red Junglefowl. It is deemed most likely, then, that the yellow skin trait in domestic birds originated in the Grey Junglefowl.

The chicken is one of the most common and widespread domestic animals. With a population of more than 24 billion in 2003, there are more chickens in the world than any other bird. Humans keep chickens primarily as a source of food, consuming both their meat and their eggs.